Grinding machine



Sept. 3, 1940. KfzwlcK GR'INDING MACHINE 5 Sheets-Sheet l.4

Filed March 17, 1959 P .GE

.l Sept. 3, 1940. K zwlcK GRINDING MACHINE s sheets-sheet '2 Filed march 17,` 195s l/n venia/- Kur? Zwick` I sept. 3, 1940.l K. zwlCK 2,213,156

GRNDING MACHINE Merch 17, s sheets-Sheet /n venlor i "Kunzwack BY sff/aw holding parts, etc., has had to'be moved back and I Speel? Jl70 each Othel- 20 forth during the grinding of the tools, Whether To these and other ends the invention resides cylindrical or conical. in certain improvements and combinations of An object of the present invention is to provide Parts all es Will be hereinafter m01`e fully dea generally improved and more satisfactory scribed, the novel features being pointed out in grinding machine which is free of the' abovethe 'claims at the end of the specification. 25

mentioned objections. In the drawings! Another object is to provide a, grinding ma- Fig. 1 is a` side elevation With parts in vertical chine which will grind cylindrical rotary tools Section of e' grinding machine in accordance With the greatest accuracy, without the need for With a preferred illustrative embodiment of the using gauges to insure proper settings for true. 'Present lnvonlflon 30 cylindrical grinding, and which is nevertheless Flg-zlsa'plan thereof? and easily used also in grinding conical rotary tools, Flg- 3 is an elevatlon of somo of the ports or tools of other forms shown in Fig. 1, viewed from a different direction.

Still another object is the provision of a grind- The same reference numerals throughout the l ing machine in which the Work to be ground ,may Several VloWS ludloato the Same parts- 35 be changed from a cylindrical rotary tool to a In the maohlne Shown lll the dluWlngS as a' `40 grinding of a-conical tool has been finished and proxlmately horizontal splndle l5 of a grinding 40 tool may be moved past a grindingv Wheel in a di`- tatou by any Sultable means' 5,5 tools'only a relatively small mass of holding feed controlled by the hand-wheel( or crank 23. 55

Patented Sept. 3, 1,940 2,213,756

u NiTED .STATES PATENT orrice GRINDING MACHINE Kurt Zwick, Munich, Germany, assignor to Friedrich Deckel, Munich-Prinz Ludwigshohe, Germany Application March 17, 1939, Serial'No. 262,410

In Germany March 5, 1938 19 Claims. (Cl. 51-122) This invention deals with a grinding machine, parts, etc., is moved back and forth, the other and more particularly with a machine capable of holding parts having additional mass being movgrmding rotary tools, although articles otherv able back and forth only when conical or other than tools as Well as tools not of the rotary type non-cylindrical grinding is required. l

5 may also be ground. i A still further object of the invention is the 5 Prior machines which have been adapted to provision of a grinding machine having means grind both' cylindrical rotary tools and conical for Supporting work to be groundl and'movine-t rotary tools have been open to various objections. past agrinding wheel, which meehS, although 0i Setting the machine for grinding truly cylindrical relatively light and convenient form, has sui- 10 tools has usuauy required the use oi gauges or cient range of vertical movement so that the 1o other measuring instruments Which are cumber- Work may be bIOllghi inO CQODeIetOII With either some and time-consuming, and the slightest inthe lower edge or the upper edge or any desired accuracy in such setting has resulted in grinding intermediate Dart 0f the grinding Wheel, eVell a tool somewhat conical instead of truly cyiindri- When a grinding wheel of relatively large diame- 15 cal. Furthermore, the adjustment of such mav13er iS employed l5 shines has had to be changed whenever the grind- A Still further object is the provision of a ing of a conical tool was finished and the grindgrinding machine in Which the Werk-holding ing of e, cylindrical tool was to begin, andvice means is so arranged as to be capable of two versa. Also, a relatively large mass of slides, vertical adjustments vwhich are additive with reconlcal rotary tool, or vice versa, with the utmost p felerl'ed lllustl'al'lye embodlmont ofl the lul/ou ease and Without requiring any special eiort to tlon there l5 Proylded a' base ll on Wlllol'l lsoll obtain a correct cylindrical setting when the upwardly oxtendmg Support '3 oarrylug the up' when it is again desired to grind a cylindrical tool. Wheel ll Wl'lloll ma'y bo ol any sultable form A further object is the provision of a grinding Suolo as an annular gl'lndmg Wheel Somewhat machine so arranged that a cylindrical grinding. cup'sllaped or tub'shaped' The Spmdle ,515 lo' rection exactly parallelto the rotary axis of the All another oouvolllem" Place on the loose l l 45 tool, to insure accurate cylindrical grinding, Wij-,1L preferably directly in front of the spindle I5, 1s a out .the necessity ofl any special setting for the 'Slide 2l-mo1mted for horizontal movement in a purpose of securing this parallel relation, and direction generally toward and away frOm Jhe also having provision for moving other non-cylingrinding Wheel I7. Preferably the Slide 2| mOVeS 53 drical types Aof tools (such as conical tools) past in the direction of a vertical plane passing along 50 the grinding Wheel in directions at an angle to the axis of the spindle l5, though deviation from i their axes. this relationship is possible without departing A further object is the provision of a machine from the invention? The slide 2| is moved by in which, when operating upon cylindrical rotary any suitable means such as a common screw the lug 29.

The parts for holding the tool or other work to.I

. Mounted on this turn-table 25 is a second slide 21,A accurately guided for movement in a straight line, the guideways preferably being provided with ball or roller bearings yor other suitable antifriction means -28 so that the slide 21 may move smoothly and easily with respect to the turntable on which it is mounted. By turning the turn-table 25 on` the slide 2|, the direction of movement of the slide 21 can be brought to any desired angular relation to the direction of movement of the slide 2|.' Usually the turn-table 25 will be so placed that the slide 21 moves approximately transverse to-the direction of movement of the slide 2|, and such a relationship is shown in the drawings.

' Suitable means is provided for clamping4 the slide 21 at any desired position along its range of travel, and for limiting its travel to any desired length. Such clamping means preferably includes' a fixed lug 29 projecting from one side of the turn-table 25, and a pair ofadjustable lugs 3| mounted on the slide 21 on opposite sides of For instance, the lugs 3| may be mounted on bolts 33 which have heads received in and slidable along an undercut or T-shaped slot -35 running along approximately the full length vof the slide 21. Clamp nuts 31, preferably provided with suitable handles as shown, are threaded on the outer ends of the bolts 33. When these are loosened, the bolts 33 may be moved to any desired position along the slot 35,

and when these'nuts 31 are tightened, the bolts 33 and the adjustable lugs 3| which they carryl are clamped in xed position with respect to the slide 21.

When thel lugs 3| are clamped -at some distance from each other, the slide 21 may move in one direction or the other until one lug or the other hits against the cooperating stationary lug 29 on` the turn-table. 25. If it is desired to hold the slide 21 immovable on the turn-table preventing any longitudinal movement, then the two adjustable lug-s 3| are brought close together and clampedtightly against opposite sides of the lug 29, so that no movement of the slide 21 relatively to the turn-table 25 is possible.

On this slide 21 is mounted a second turntable 4|. lPreferably, however, the turn-table 4| has an approximately vertical axis of 'rotation which is not xed with respect to the slide 21,

f but which may 'be shifted to various positions along the slide 21. This may be conveniently accomplished by mounting the turn-table 4| on k a base 43 which is slidable along the top of the slide 21 in a lengthwise direction thereon,'and which is secured in any desired position on -the slide 21 by means of bolts 45 passing through the base 43 and having heads engaged in an undercut or T-shaped slot 41 in the slide 21. The turn-table 4| turns onl the base 43 about an approximately vertical axis which is fixed with respect to the base.

Rising from the turn-table 4| is an upwardly extending post or pillar 5|, provided with an approximately vertical'guideway on which is slidably mounted a vertica1 slide 53 controlled in'lts upward and downward movements by any suitable feeding means such as the feeding screw' 55 mounted on the slide 53 and held against longitudinal movement with respect thereto, and which has a threaded part engaging the threads of a nut 51 held stationary in the pillar 5| by suitable means such as a set screw 59. A handwheel or crank 6| on the screw 55A may be turned to raise or lower the slide 53`with respect to the pillar 5|.

l0 The slide 53 includes a skirt flange 1 or canopy 63 which encloses the upper part of the pillar 5| and protects the screw feed parts 55 and 51 from grinding dust orfother foreign matter.

Mounted on one side of the vertical slide 53 is a support 1| capable of being rotated relatively to the slide 53 about the axis indicated by the dot dash line 13 in Fig. 1, this axis being indicated at the point of crossing ofthe two dot dash lines 13a in Fig. 3. In effect, this support 1| is a turntable oscillatable for adjustment about a substantially horizontal axis with respect to the slide 53 on which it is mounted. It is clamped in any desired position on the slide 53 by clamp-- 83 pass through holes in these anges 8| and have heads in arcuate T-shaped slots formed in the bracket 15, so that by loosening the nuts on these bolts, the carrier 19 'may be tilted to any desired angle (within asubstantial angular range of travel of approximately 90) with respect to the bracket 15, and then may be clamped in any desired position by tightening the nuts on the bolts 83. Frequently the rotary support 1| will be clamped to the slide 53 in such position that the shaft 11 is approximately horizontal, and this is the position shown in the drawings, but by turning the support 1| with respect to the slide 53. the shaft 11 may be tilted in either direction to a substantial angle to a horizontal plane, if the work to be ground is of a character where such an angle is advisable.

-The bed or carrier 19 is provided with a guide'- way extending in a diriection preferably parallel to the shaft 11, and a work slide 9| is mounted for movement along this guideway. As in the v case of the guideway between the parts 25 and 21, this guideway between the parts 19 and 9| is preferably provided with ball bearings, roller bearings, or other anti-friction means 92 so that the work carriage 9|, although guided accurately for perfectly straight movement, is able to move freely and easily along its path of travel. It may be clamped in fixed position relative to the carrier 19, or allowed any desired range of tmovem ent thereon, by means of a clamping arrangement substantially the same as that used between the parts 25 and 21. That is, there are a fixed lug 93 formed on the slide 9| and a pair of cooperating adjustable lugs 95 lying on oppositte sides of the` lug 93 and capable of being clamped' in different l positions on the carrier 19, in a manner substantially the same as the adjustable lugs 3| previously mentioned.

On Athe work slide 9| there is suitable means for holding the work to be ground by the grinding wheel Il. Conveniently, the slide 9| may be providedwith a dove-tailed portion 10| running lengthwise of the slide 9| in a direction parallel to the direction of movement of the slide 9|. On this'dove-tailed portion |0| may be clamped the means for holding the work to be ground. When rotary cutting tools (whether cylindrical or conical) are to be ground, the holding means may comprise a clamping head stock |03 of any convenient construction, and a tail stock |05.

The head stock |03 is provided as usual, with any suitable arrangements for clamping the shank of a rotary cutting tool, such as the cylindrical reamer shown at Il in Fig. 2, and for turning this shank from time to time by any desired increments, while the tail stock is provided with the usual conical pin on which the opposite end c-f the rotary cutting tool Il may be centered.

The dove-tailed track |0| on which the head stock |03 and tail stock |05 are mounted is constructed so as to be exactly parallel to the direction of the guideway on which the slide 9i moves with respect to the carrier 19. The headstock |03 and tail stock |05 are so constructed that the axis of any rotary cutting tool properly clamped in the head stock |03 and centered in the usual manner on the pin on the tail stock |05, is exactly paralle1 to the dove-tailed track |0| and, consequently, exactly parallel to the direction of movement of the slide 9| on the carrier 19.

If tools other than rotary cutting tools are to be ground, the head stock |03 and tail stock |05 may be removed from the dove-tailed track |0| and any other suitable clamping means adapted to hold the tools to be ground may be applied to this dove-tailed track. The same is possible when articles other than tools are to be ground.

It will be seen that the machine in the illustrative form herein described as a preferred embodiment ofthe invention, has many and important advantages over tool grinding machines of the Aprior art. The parts, although capable of a great variety of adjustments to different positions, are compact and relaitvely light, thus not being open to the objection of heavy and cumbersome parts present in so many prior machines, which by their Weight and size make operation diflicult andwhich require'heavy and expensive frame work for supporting them. l

rIn spite of the lightness and compactness of the present arrangement, it is capable of adjustment through a wide range. For certain types of grinding, it is desirable' to be able to bring the work at one time into contact with the lower edge of the grinding wheel |1 and at another time into contact with the upper edge thereof.

/With the modern tendency toward the use of still be kept small while achieving -this resulta?- If the 4vertical range of movementiof the slide 53 on the pillar 5| is not suflicient to shift the Work from the bottom edge tolthe top edge of the grinding wheel, then a still further vertical movement may be attained by' turning the carrier 19.

relatively to the bracket 15 about the axis of the shaft 11 as a center, shaft being placed roughly horizontally by suitable adjustment of the turn-table 1| on the slide 53. Since the tool or other work to be ground is placed at a position offset a substantial distance horizontally from the shaft 11, it follows that when the parts are turned about the shaft 11 as above indicated, the work being4 operated upon Y will be correspondingly raised or lowered through a substantial extent. This possibility of adjusting the Work upwardly and downwardly is in addition to the upward and downward range of movement of the slide 53 on the pillar 5|, and thus the work holding means may be described as capable of separate upward and downward adjustments which are additive with respect to each other, and which together resultiin a great upward and downward range of movement of the work being operated upon, in spite of a very small over-all height of the holding means.. The turning of the parts about the shaft 'l1 may be used as a rough adjustment of the height of the work, ne adjustment of the height being obtained by moving the slide 53 by means of the screw 55, which screwfr may be provided with graduations or reference marks if desir'ed.

In operation, assuming that a cylindrical rotary cutter, such as indicated at in Fig. 2, is to be ground, the cutter is centered on the tail on its corresponding support, and also'by turn- 'ing the vertical turn-table about its horizontal axis 13 if desired. The direction of the slide 21at this time is unimportant, and no pains need be taken to set this slide to any Aparticular direction. The slide 21 is, however, clamped against longituinal movement by means ofl the clamping lugs 29 ,and 3|.

All these settings may be made while the tool to be ground is kept a substantial dist ce away from the grinding wheel I1, obviating danger to the operator if the grinding wheel is in motion. Then, by turning the feed wheel 23,` the slide 2| is moved in a direction toward the grinding wheelv until the "tool I to be ground is brought against the grinding wheel |1 and to a position to make the desired. depth of cut. Then the work slide 9| is moved by hand in one direction or the other along its guideway on thesup- 4 port 19, carrying successive portions ofthe tool past the grinding wheel in cooperative relation thereto. Since the movementsl of the slide 9| may be performed by direct manual pressure, the grinding operation is under the sensitive control of the operator and subject to his direct feel sov that best results can be attained.

It is to be especially noted that this grinding of cylindrical cutters does not require any special or complicated setting of the holding mechanism in order to obtain trulycylindr'ical grinding, and especially it` does not require the use of gauges or indicators or g'raduations, as required in many of the prior art devices, in order to insure Apar- -allel setting and accurate cylindrical grinding.

The mere fact of centering the tool properly with respect t'o the head stock |03 and tail stock I 05 automatically insures the axis of the tool being parallel to the' direction of movement of .the s1i de,9| on its guideway, and automatically insures the correct cylindrical grinding-of the tool Without any possibility of accidental conical grinding.

When a conical cutter is to be ground, then it 75 i is clamped in the head .stock 03 and tail stock |05 asbefore, but this time the slide 9| is heldlugs 95, and the slide v2`| is set at an angle to the axis of the conical cutting tool corresponding to the desired conical angle of thertool. 'Ihen the slide 2l is moved back and forth along its guidel Way on the member 25, this movement carrying with it all of the parts supported from the slide 21, such as the turntable 4l, pillar 5|, carrier 19, and head stock |03 and tail stock |95. As in the cas'e of cylindrical grinding,the parts arepref .erablyl'moved back -and forth by direct hand pressure, to secure greatest-sensitivity and so that the operator may get the feel of the Work as' it progresses, but screwl feeds or other mechanical feeding means could be used, if desired.'

It shouldbe notdtliatwhen grinding cylindrical tools, the parts ltofbemoved backV and forth are few and of low mass, consisting'only of the work slide 9|, head 4stockfll, tail stock |05, and the tool' being-ground.' The m'ass of the other parts 21, 4|, 5|, and '|9gremains stationary during cylindrical or parallel grinding, and must be moved back and forth only when performing conical or oblique grinding, which in many shops is not done so frequently as cylindrical grinding.

Another noteworthy feature is that when the grindingof a'conical cutter has been completed, if it ls desired to grind a cylindrical cutter, this may be done without resetting the mechanism. Slide 2'!` may be left in any angular position to which it was previously set for grinding the conical tool (being clamped, of course, against movemerit by. means of theclamps 3|) and Without 'any change in' thisposition of the slide v2`|, the

cylindrical tool may now be ground by moving the slide 9| back and forth on its carrier 19.

Thus a grinding machine of the utmostflexibility and at the same time with great simplicity and vcomp'ac'tness is provided. The many advantages of this construction over the prior avail- 4able constructions will be readily seen by those skilled in lthis art upon a careful study of 'the present constructiorrnand its adaptability to practically any grinding problem will be apparent,v although the machine is especially useful, as above indicated, for grinding` rotary -cutters of either the cylindrical or the conical type. Although grinding has been referred to, it will be understood that a millingtool or other cutting tool could besubstituted for the .grinding "5' Wheel without otherwise altering the prin- 5 vand forth lalong a path of travel capable of adjustment, to various angular positions with respect to said grinding Wheel axis, a second slide supported from said first mentioned slide and capable ofl movement back and forth along Va ing a normal grinding operation against movement in any-direction except along said path of travel of said 'first mentioned slide, and means on said second slide for holding a rotary tool to be ground in a position withits axis in denite fixed relation to'said grinding Wheel and. parallel to said path of travel of said second slide, so that when a cylindrical rotary tool is mounted in said holding means, accurate cylindrical grinding thereof may belinsured by holding said first mentioned slide against movement and by moving said second slide through its said path of travel to carry the tool past said grinding wheel in cooperative-relation thereto, and When a conical rotary cutting tool is mounted in said holding means, it may be ground by adjusting the paths of travel of the two-,slides to the required angle with respect to each other and by carrying the tool past said grinding Wheel in cooperative relation'thereto by moving said rst mentioned slide along its path of travel while maintaining said second slide in fixed relation .to said iirst mentioned slide. l

2. A grinding machine capable of grinding rotary tools, includingfa grinding lwheel rotatable about an axis, a slide capable of movement back and forth along a path of travel capable of adjustment to various angular positions with respectto said grinding wheel axis, a second slide .supportedfrom said rst mentioned slide and capable of movement back and forth along a path of travel capable of adjustment vto various angular positions with respect to said pathof travel of ysaid first mentioned slide and held during a normal grinding operation against movement in any direction Aexcept along said path of travel of said iirst mentioned slide, and means on said second slide for holding a rotary cutting tool to be ground, said holding means being adjustably mounted on said second slide to be capable 'of holding cutting tools of different sizes and being so constructed that in every position of adjustment of said holding means a rotary cutting tool held thereby has its axis in fixed parallel relation to said path of travel of said second slide.

3. A grinding machine capable of grinding rotary tools, including a grinding wheel rotatable about an axis, a slide capable of movement back and forth along ya path of Ytravel capable of adjustment tov various angular positions With respect tosaid grinding wheel axis, a second slide supported from said first mentioned slide.

and capable of movementback and forth along a pathof travel capable of adjustment to various angular positions-with respect to said path of travel of said rst mentioned slide, a headstock and a tailstock mounted on said second slide for holding a rotary tool in position to 'be ground by said 'grinding Wheel, atv least one of said stocks being movable toward and away from\ the other sogas to accommodate tools of different lengths, said stocks in all positions thereof serving to maintain a rotary tool held thereby with its axis parallel to the path of the travel oi said second slide.

4. A grinding machine'as described in'claim 2,

further including means for holding eitherlof said slides against movement along its respective path of travel.

5. A grinding machine capable of grinding rotary tools, including a griding Wheel rotatable path of travel, capable ,of `adjustment to varus-c {l'bQllt all aXiS. 2 lSi -Sld mflunted fOI ipangular positions with respect to said path of travel of said first mentioned slide and held 'durprdmately horizontal-movement in a direction approximately -towad and away- `from vsaid grinding wheel, a second slide supported from said iirst slide for rotation relative thereto about an approximately vertical axis and also for approximately horizontal rectilinear movement relative thereto, a work slide supported from .said second slide for rotation relative thereto about an approximately vertical axis and also for rectilinear movement relative thereto, and holding means on said work slide for holding a rotary tool to be ground in a position to be acted upon' by said grinding wheel and with its axis parallel to the direction of said "-rectilinear movement of said work slide.

6. A grinding machine capable of grinding rotary tools, including a grinding wheel rotatable about an axis', a first slide mounted for approximately horizontal movement in a direction approximately toward and away vfrom said grinding wheel, a second slide supported from said rst slide for rotation relative thereto about an.

approximately vertical axis and also for approximately horizontal rectilinear movement relative thereto, a work slidesupported from said second slide for rotation relative thereto aboutan approximatelyl vertical axis and also for rectilinear movement relative thereto, holding means on said work slideA for holding a rotary tool tobeground in a position to be acted `'upon by/said grinding wheel and with its axis parallel to the direction of said rectilinear movement of4 said work slide, and means `interposed between said first slide and said work slide for raising and lowering saidu work slidev with respect to -said- 7. A grinding machine capable of grinding rotary tools', including a grinding wheel rotatable about an axis, a first slide mounted for approximately. horizontal movement in a direction approximately toward and away from saidl 40 grinding wheel, va second slide supported from said rst slide for rotation relative thereto about an approximately vertical axis andv also for approximately horizontal rectilinear movement rel-1 ative thereto, a work slide supported from said` an approximately vertical axis and also for rectilinear movement relative thereto, holding means-on said work slide for holding a rotary tool to be ground in a positionto be ,actedl upon 50 by said grinding wheel and with ints axis parsecond slide for rotation relative thereto about allel to the direction of said rectilinear move-` ment of said work slide, andtwo means interposed between said iirst slide and said work slide for raising and lowering said work slide 55 with' respect to said rst slide, said` two means being additive with respect to each other.

A grinding machine as described in claim '7, in which one'of said two/means` includes a slide mounted for approximately vertical movement.

9. A grinding machine as described in claim 75 tending in 'a direction generallyntransverse totravel.

said direction of rectilinear movement of said ported from said rst slide for approximately horizontal rectilinear movement relative theref to, an oscillatable connection between said first slide and said second slide so that the direction of rectilinear movement of said second slide may 'be swung about an approximately vertical axis to various positions with respect to the ldirection of movement of said rst slide, an upstanding pillar mounted on said second slide `for rotaryA adjustment relative thereto about an approximately vertical axis, a third slide mounted for upward and downward movement on said pillar, a worktslide supported from said third slide for rectilinear movement relative thereto, and means on saidwork slide for holding a rotary tool in a position to be acted upon by Isaid operating element and with its axis parallel to the direction of rectilinear movement of said workslide.

12. A machine as described in claim 11, iurther including an oscillatable connection between said third slide and said work slide so that the direction of rectilinear movement of said work. slide may be adjusted relative to the direction of movement of said third slide by swinging it about an axis approximately perpendicular -to both of said directions.

13. A machine as described in claim 11, further including an oscillatable connection between said third slide and said work slide so that the position of a tool held by said work slide may be altered relative to said third slide by.I

swinging said work slide relative to said third slide about an axis spaced, from and approximately parallel to the axis of said tool.

" 14. A machine as described in claim 11, fur-u ther including a slidable connection between said pillar and -said second slide so that said pillar may be adjusted to various positions along the length of said second slide.

l5. Aimachine as described in claim'll, further including means for holding any one of said slides against movement along its path of 1s. A machine as described in daim 11, lin vwhich said second slide and said work slide are both provided with anti-friction bearings means l said support, a carrir'mounted on said slide for oscillation with respect to said slide about an approximately horizontal axis, a member mount- 'ed on said carrier for oscillation with respect to said carrier about an axis lapproximately perfpendicular to the axis-of oscillation of sai 4 carrier, a work slide mounted on said member forrectilinear movement along' a line .parallel to 'the axis of oscillation of said member, 'and means onY said work slide for holding. work in position to cooperate with and be ground by said grinding v wheel.

erov

19. A machine for grinding tools and the like, said machine including' a grinding wheel, a support, a slide carried from said support and movable approximately vertically with respect to said support, a carrier mounted von said slide for oscillation with respect vto sai'dslide about an approximately horizontal axis, a member mounted on saidv carrier for oscillation with respect to said carrier about an axis approximately perl0 vpendicular to the axis of oscillation of said carrier, and a head stock and tail stock-supported from said member with their centers at equal distances from the axis of oscillation of said member for holding an elongated rotary tool n KURT ZWIC. 

